A comparison of scutellum callus and epiblast callus induction in wheat: The effect of genotype, embryo age and medium

All 35 randomly chosen cultivars of Triticum aestivum produced both epiblast callus and scutellum callus, indicating that the capacity to form callus from these two origins is common in this wheat. The induction frequencies of the two calluses varied considerably between different genotypes, ranging from 28% to 96% for scutellum callus and 18% to 94% for epiblast callus. T. aestivum varieties on average formed scutellum callus at a higher frequency than epiblast callus and no correlation was observed between the induction frequencies of the two calluses. T. durum formed only scutellum callus. Although maximum induction of embryogenic epiblast callus had previously been shown to occur at stages II and II of the embryo development, the highest induction of embryogenic scutellum callus occurred at stages I, II and III. The concentration of macroelements in the MS medium affected the induction frequency of embryogenic callus from both scutellum and epiblast. Both scutellum and epiblast callus formed typical embryoids but at a low frequency. The epiblast callus was clearly differentiated from the underlying tissue and therefore the meristematic tissue could readily be separated from non-embryogenic tissue. The embryogenic scutellum callus, on the other hand, was always mixed with some non-embryogenic tissue and could not readily be separated. The scutellum callus was generally larger than epiblast callus and produced more plantlets.